A reaction product, obtained through ethylene polymerization, is composed of unreacted ethylene, a solvent necessary to dissolve a catalyst and ethylene upon polymerization, and linear α-olefins having various numbers of carbon atoms polymerized through the reaction, and such an effluent stream (reaction product) is separated into a target product via multiple recovery towers. FIG. 1 shows a typical process of separating an ethylene polymerization effluent. As shown in FIG. 1, the effluent stream is separated and purified by being passed through an unreacted ethylene separation tower (not shown), a C4 separation tower 2 (or a butane separation tower) and then a C6 separation tower 4 (or a 1-hexene recovery tower). Here, the bottom liquid discharged from the bottom of the C4 separation tower 2 is supplied as a feed for the C6 separation tower 4, and the temperature of the feed stream is higher than the temperature of the tray positioned at the bottom of the C6 separation tower 4, and thus a load is applied to a condenser 6 connected to the C6 separation tower 4, ultimately increasing energy consumption and associated costs. That is, since the temperature of the feed introduced into the C6 separation tower 4 is higher than the temperature of the tower itself, an excessive load is applied to the condenser 6. Hence, to remove heat in order to solve such problems, a utility such as cooling water is excessively used, thus increasing operating costs.
Meanwhile, using the high temperature of the feed, the feed may be supplied to a tray located lower than the tray of the C6 separation tower 4 to which the feed is originally supplied, in order to solve the above problems. In this case, however, the composition distribution in the tower is affected, and thus limitations are imposed on improving energy efficiency by controlling the feed stage of the tower to which the feed is supplied. Therefore, with the goal of solving the above problems, a method of efficiently separating effluents produced through ethylene polymerization using a small amount of energy is required.